Well, the biggest draw for me to the Kindle store is the selection. You mentioned in your OP that "Kindle fanatics" seem love the amazon e-book store more than they should. Well, you know, since you don't own a kindle, no wonder you don't love the Kindle store.
But people who have a Kindle, love the Amazon site because for us, we don't have a problem getting our books onto the Kindle!! Also, most of the books you selected for the experiment were sci-fi, by the way. In my experience, fictionwise caters more towards sci-fi titles in their selection, but I could be way off base on that one. Just my observation.
I think Amazon has the best selection overall. I know some may hate Amazon, but the fact is that they have a broader selection--which is the very reason some people hate on them. Hating something because of the hype is understandable, but facts are facts. Unless I am wrong, then I don't know my facts. Which could be a fact.
Now, I do most of my reading on a Sony Reader 300. But I have a Kindle, so for me, the amazon store is the best place to buy ebooks. Many, many times I have seen a book on Amazon that I liked and then checked around, but the other stores just don't have it or it's more expensive.
So basically, I'm saying you have a flaw in your argument about Kindle fanatics going ga-ga over the store. If you are a non-kindle owner, there is no reason for you to enjoy the Amazon store because it's harder for you to buy books. For Kindle people, on average, it's just easier to stick with Amazon--because of selection and ease of reading right away
Now, there are exceptions, but selection-wise, it seems that the publishers gravitate towards Amazon. Irritating to some, yes, but a fact nontheless.
Now having said that, I hate the Topaz format. Because I like to own my books and be able to read them on any device. But that's another argument and I just don't buy Topaz books because I cannot liberate them from their heavy chains of woe...